Each year numerous people are injured by the use of hazardous cleaning solvents. These injuries typically occur because the cleaning solvent employed forms explosive compositions when its vapors are mixed with air and are accidently detonated, or because the volatile cleaning solvent is toxic and workers exposed to the toxic vapors receive an unhealthy dose.
Elimination of these toxic and/or combustible solvents is not an acceptable alternative since many the solvents cannot be adequately substituted. Likewise, the restricted use of these solvents in protective chambers or hoods is not acceptable because of the prohibitive cost of such chambers or hoods and because of the limited mobility associated with their employment.
The hazards involved in using cleaning solvents are accentuated in vapor cleaning processes. In a typical vapor cleaning process, vapors of the cleaning solvent are passed over the part or mechanical device sought to be cleaned. At this point, at least a portion of the vapors are condensed on the part or device to constantly bathe it in fresh cleaning solvent. The condensed solvent drips from the object carrying with it the contaminates. The point at which the vapors contact the atmosphere poses the threat. For example, if the vapors are combustible they form explosive composition at this vapor-air interface. Also some of the vapors which are not condensed may escape the surrounding area, depending upon its toxicity, could pose a health threat to workers in the area.
Vapor cleaning is particularly useful in cleaning glass and plastic lenses where spot free surfaces are essential. Water when it evaporates from the lens surface forms spots which adversely interfer with the true optical performance. These spots are caused by water-soluble salts contained in the water. Even trace amounts of these salts result in undesired water spots. However, the use of distilled water is not satisfactory since water tends to leach small amounts of salts from glass and other types of materials. The use of cleaning solvents such as acetone can achieve a highly spot free surface. Acetone, on the other hand, can form an explosive mixture with air and accordingly is hazardous to use.
A need therefore exists for reducing the hazards associated with the use of heretofore hazardous solvents, which does not limit the mobility and usefulness of the cleaning apparatus, which can be readily used, which is inexpensive to manufacture and operate, and which can be used in vapor cleaning systems.
It is an object of this invention to provide an improved method for vapor cleaning a solid substance.
It is an additional object of this invention to provide an improved vapor cleaning apparatus.
It is an additional object of the invention to provide a method and apparatus for safely vapor cleaning a solid substance with a hazardous volatile solvent.
Other additional objects of this invention will become apparent from the attached drawing, the following description of the invention and the accompanying claims.